1. Brief Description of the Invention
The present invention relates to low-cost, efficiently-manufactured, polymer-based products useful as tab-type strip shingle roofing products as well as for other uses. The inventive shingles are weatherproof, inexpensive to manufacture, and durable, particularly as contrasted with conventional shingles in areas of the country subject to hail damage. In such uses, the inventive roofing shingle products will have an average life far greater than that of current commercial roofing shingles, which are made using fiberglass or asphalt.
The invention also includes a method of making such products. In a preferred embodiment, products of this invention use rubber material as the polymer base in combination with specific types of polyolefins. The rubber material can be most efficiently provided by the use of "crumb rubber" particles ground from spent automobile tires and other recycled rubber debris, which are readily available and of very low cost.
2. Description of the Prior Art
General
The market for construction roofing products, including tab-type strip roofing shingles, is very large. Each year, several million new homes are built in the United States and Canada utilizing sloped roofs with roofing shingles, and additional millions of existing homes have their roofing materials replaced. A majority of all North American slope-roofed private homes employ tab-type strip roofing shingles.
Commercial roofing products, other than very expensive slate, tile, or cedar wood products used for very high end houses, are today either asphalt or fiberglass based. The use and manufacture of these products including the expense of raw materials, damage from the consequences of the use of highly combustible raw materials in their manufacture, surprisingly quick degradation when exposed to the elements and consequent short useful life, and in the South and Southeast, high levels of actual breakage caused by hail, have caused much concern.
The construction industry has therefore long sought a competitively priced, relatively low-cost, roofing product that could be efficiently manufactured to sell into this multibillion dollar-per-year North American market without the problems described. Scientists and practical construction industry management have long searched for a roofing product that used cheaper and better raw materials than such traditional materials as asphalt and fiberglass, which comprise almost all such commercial products in the present day.
The search for such new products has, up to now, also unsuccessfully looked at the potential for use of a major American waste product, which itself has not found commercial uses at anything approaching the volumes of waste materials produced. For almost as long as rubber tires have been manufactured, the question of finding an acceptable use for worn-out tires has stimulated invention. References to the history of this development are set forth in U.S. Pat. No. 4,851,500, where recycling patents as old as 1957 are cited, with "related" patents as old as U.S. Pat. No. 1,550,968 (1925). Similarly, the concept of recycling rubber tire material by grinding such material into small pieces is quite old. U.S. Pat. No. 3,210,301 discloses two improvements for reducing the processing time of recycled rubber used for rubber compounding and describes the recycling use in 1965 as already "well known". A 1978 U.S. Pat. No. 4,125,578 describes a heat process for reclaiming vulcanized crumb rubber from tires.
Interestingly and somewhat strangely, the use of large geometrical pieces of tires as roofing is similarly old. U.S. Pat. No. 3,803,792 for a "Tire Roof" discloses the construction of a roof covering made from cut and segmented waste tires, providing in effect a tile roof where the tiles are segments of tires. Work has continued in this unusual area of the use of cut-up tire segments up to the present day, with improvements in the configuration of the tire segments shown in U.S. Pat. No. 5,086,552 and U.S. Pat. No. 5,675,954 as recently as October, 1997. In none of these patents is any consideration shown of the possibility of the creation of a new roofing product from particles of tires and other materials. Similarly, there is no consideration shown of the utility of small (millimeter-sized) pieces of ground tire material.
The general concept of using small pieces of rubber, such as crumbs from the recycling process, to add desired characteristics to other materials is known. U.S. Pat. No. 4,109,041 (1978), as a representative example, teaches the use of waste rubber particles in making non-slip coatings on construction panels.
Several patents as to the reuse of recycled tire waste to make various types of sheet goods, including roofing sheets, were filed starting in the 1950's. These early patents, and their more modern progeny, use heat and thermosetting agents to create molded articles. For example, U.S. Pat. No. 3,027,599 discloses a method of molding articles from scrap tire material, using a thermosetting binding agent. U.S. Pat. No. 3,267,187 discloses the use of crumb rubber (not specifically from scrap tires) in formed, resin-fused textured sheet flooring. U.S. Pat. No. 3,844,668 generally shows the use of recycled rubber from whole tires, reacted at high temperatures with asphalt, and then dissolved in kerosene or a similar hydrocarbon, to repair pavements or roofing.
Other patents utilizing rubber utilize crumb rubber to make rubber sheet goods or similar goods which might be used on roofs. One set of patents demonstrate attempts to obtain useful materials from rubber ingredients by essentially using pressure alone. U.S. Pat. No. 5,527,409 discloses a log-like structure created from pressed crumb rubber which is spirally sliced into sheets (with a separate waterproofing compound to be added after installation)--the patent does not disclose any elastomer or other blending additives and describes the only bonding mechanism as being pressure.
Another group of patents deal with batch-type molding or casting processes for making recycled rubber roofing products involving extensive curing (i.e., polymerization), in contradistinction to a continuous-type extrusion process followed by at most limited curing. U.S. Pat. No. 4,028,288 shows a heat and pressure-molded mixture of ground tires, including the fibrous tire cords, and a synthetic thermoplastic resin. The patent identifies a useful synthetic thermoplastic resin as comprising at least one of the materials polyethylene, styrene, and polypropylene.
U.S. Pat. No. 4,795,603 describes a process of mixing rubber waste and crushed rugged molded polyethylene or polypropylene wastes together, and heating, pressing, and injecting them so as to mold them. The injection moulding composition is described as useful for batch-type molding processes, rather than a continuous extrusion-type process.
U.S. Pat. No. 4,851,500, previously discussed, shows the use of scrap rubber, sulfur and pressure to make a cured rubber product for use as roofing products such as roll roofing, tiles, shakes and slates, and other materials. The patent describes this use as an improvement over prior art because it uses pressure rather than a working and plasticizing action such as a screw; it also requires the use of sulfur. For background, Bertolino published European Patent Application 0 401 885 is similar, in that it emphasizes the admixture of waste rubbers, plastics, and fibers, mixed with polyethylene or another thermoplastic, and then heated by an extruder or any other similar system.
U.S. Pat. No. 5,254,405 and its continuation-in-part, U.S. Pat. No. 5,385,953, teach the embedding of crumb rubber in a polyurethane matrix. U.S. Pat. No. 5,258,222 utilizes crumb rubber in a cast, tile-like roofing product which is liquid, and cures after pouring. The patent teaches the requirement of epoxy resin or neoprene to hold the other materials together along with silica and other materials.
Three related patents (U.S. Pat. No. 5,453,313, its continuation U.S. Pat. No. 5,580,638, and its continuation-in-part U.S. Pat. No. 5,525,399) disclose the use of polysulfide together with rubber for structural strength. The continuation patents add fire retardant and ultraviolet protection compounds, and an asphalt matrix. The process which is common to all three patents requires in addition to polysulfide, extensive curing.
U.S. Pat. No. 5,635,551 discloses an improvement in the molding of articles using pulverized recycled tires by specifying a limited range of thermoplastic resins. The patent requires the use of five additional ingredients (starch, acetone, caustic soda, glass wool and ammonium phosphate) with starch, which must comprise at least 5% by weight of the finished composition, having the highest percentage requirement.
A number of alternate technologies for creating materials which gain their strength and hardness from covalent chemical bonds with crumb rubber have also been attempted.
U.S. Pat. No. 4,244,841 utilizes sulfur and zinc stearate as a cure mix to form a rolled product one inch in diameter suitable for roofing, and requires sulfur to achieve its result. U.S. Pat. No. 4,970,043 shows the use of a "cohesive base material" such as a styrene-butadiene block copolymer, and a minimum of "at least" 50% ground rubber. The patent also involves the recycling of exclusively high grade rubber.
U.S. Pat. No. 5,010,122 describes a thermoset composition comprising crumb rubber having a size less than 10 mesh, a thermoplastic material which can include olefinic polymers with blends of similar polymers, and one or more coupling agents. Bonds are caused by reactions with the coupling agent bonding the crumb rubber and olefin polymers together. The patent describes the requirement of at least one coupling agent, and covalent bonds or equivalent chemical bridges between the rubber and the thermoplastic material. The patent specifically identifies silane coupling agents to form the required covalent bonds.
The concept of a polyolefin sheet material for roofing, like that of a rubber material for roofing, is not new: see for example U.S. Pat. No. 5,256,228. U.S. Pat. No. 3,547,674 (1967), claims the use of asphalt to anchor a polyolefin fabric, with more asphalt anchoring individual crumb rubber pellets attached to the fabric.
There are a number of patents which utilize rubber plus an olefinic substance, but none of them envisions the use of crumb rubber. Rather, they concern polymerization reactions between specific rubber compounds and olefin or polyolefin compounds, generally with high initial crystallinity or with a crystallinity promoter, and generally require other specific chemicals appropriate to the particular polymerization reactions being described. See U.S. Pat. No. 4,311,628 which describes a blend of polyolefin resin and particles of EPDM rubber of a size below 50 microns average, cured using phenolic compounds. U.S. Pat. No. 5,157,081 teaches a vulcanized rubber in a crystalline polyolefinic resin matrix. Rubbers useful are listed as bromobutyl rubber, chlorbutyl rubber, butyl rubber and mixtures thereof with curing required with a non-peroxide curing system. U.S. Pat. No. 5,290,886 adds low molecular weight ester plasticizers.
U.S. Pat. No. 5,389,715 claims an uncured sheet polyolefin polymer roofing product which is made semi-self-sealing by curing in place on a rooftop through the inclusion of a "cure package." U.S. Pat. No. 5,594,073 claims a roofing composition involving blends of two specific rubbers, a narrowly-defined urea composition, sulfur, an accelerator, and a cure activator.
A patent which teaches the use of rubber in roof shingles, U.S. Pat. No. 5,338,783, teaches the requirement of silicone rubber, silicon dioxide, and aggregates to make tab shingles.
There are a few patents which involve extrusion processes involving crumb rubber and polyolefins. The first of these is U.S. Pat. No. 5,157,082. The patent shows a product made from 10-90 parts by weight of ground rubber, of a maximum 1.5 mm. average size, and also describes about 90 to 10 parts by weight of polyolefin resin and at least 0.5 parts by weight of one or more functionalized olefin polymers per 100 parts by weight of polyolefin resin. A second product and process disclosed require about 90 to 10 parts by weight of one or more functionalized olefin polymers. Such functionalized olefin polymers are described to be a copolymer of at least one olefin and at least one ethylenically unsaturated organic monomer; wherein said organic monomer is selected from the group consisting of unsaturated mono or dicarboxylic acids having from 3 to 20 carbon atoms; acid anhydride, maleamic acid, acid halide, ester and metal salt derivatives of said unsaturated mono or discarboxylic acids; vinyl esters of saturated carboxylic acids, wherein the acid constituent of said saturated carboxylic acid has from 2 to 18 carbon atoms; vinyl alkyl ethers wherein said alkyl constituent has from 1 to 18 carbon atoms; vinyl halides; vinylidene halides; acrylonitrile; methacrylonitrile; and styrene.
U.S. Pat. No. 5,523, 328 discloses extrusion products employing crumb rubber and polyolefin. The patent specifies that the ground tire waste must comprise rubber and metal debris. Spent tires typically comprise about 60-70 percent rubber, 20-30 percent steel, and 5-10 percent textile fibers according to the patent's specification.
While all the above described patent activity indicated a long-term scientific search to create a new type of rubber-based roofing shingle, as of this date, the inventors hereof are unaware of any commercial roofing shingle product available to the public, or under commercial development, other than asphalt and fiberglass-based shingles.